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The Point about Smoke and Olive Oils

One of the most contentious issues between olive oil and competing vegetable oils is the smoke point.

When frying the oil in the pan is heated between 160-240°C. The optimal temperature is around 180°C. Lower temperatures are used in other forms of cooking – roasting, baking etc. In Asian countries where the wok is used for stir frying, temperatures higher than this can be expected.

The importance of smoke point from a chef’s point of view was brought home to me by a chef in Blenheim, New Zealand when I quizzed him about which oil he used for frying. His answer was avocado oil because of its high smoke point, and secondly he liked the flavour. Pursued as to why he didn’t use some of the locally produced extra virgin olive oil, his answer was that he was so busy in the kitchen that he could not watch the frying all the time and the lower smoke point of olive oil often caught him out with the food he was frying being spoilt. Price was not an issue.

There is also a perception that ‘burned’ frying oil has deteriorated producing toxic and, in some cases, cancer inducing substances. Some of the deterioration products formed in fats and oils heated to high temperatures for prolonged periods are peroxides, aldehydes, ketones and hydroperoxides. Any of these can have toxic effects. Some are volatile – aldehydes and ketones – so do not get into the food, others are not absorbed by the intestine, but some are.

The bluish smoke given off at the smoke point is the aldehyde acrolein, a result of the breakdown of the glycerol associated with triglycerides. The smoke point marks the beginning of nutritional and flavour degradation and the production of free radicals. The presence of anti-oxidants helps prevent this and increases the smoke point.

The comparative list of smoke points given above is from Wikepedia. Other sources confirm that within a few degrees these figures are acceptable.

You will note that refining oils tends to increase the smoke point as impurities and free fatty acids are removed. Hence refined ‘extra light’ olive oil has a higher smoke point than extra virgin olive oil. The table shows that high quality extra virgin olive oil (evoo) has a higher smoke point than lower quality evoo – due to the presence of more anti-oxidants and low free fatty acid levels. Another selling point for high quality evoos.

Another point to consider is that when frying very little oil penetrates the food and so even if smoke point is exceeded, the toxins formed are unlikely to enter into the component that is eaten in any quantity. Drying the food after frying to remove the external oil also reduces toxin intake if the smoke point has been exceeded.

Olive oil is a good compromise on the smoke point, health and penetration issues.

As far as the loss of health attributes is concerned, tocopherols (includes Vitamin E) are destroyed or inactivated at 180°C while phenols (anti-oxidants such as the bitter component oleuropein) are more resistant to heat and will be retained at higher temperatures.

In summary on smoke point, with frying at the ideal temperature around 180°C high quality extra virgin olive oil is fine, and there are the added health attributes.